Hello everyone!
I am a 35 year old science teacher from North Carolina. I have had an amateur interest in all things science since I was very young, and now teach high school Physics and Biology. I worked for many years as a field biologist before becoming a teacher, with a focus on threatened species of the southwest such as the Mojave desert tortoise. My proudest achievement so far from a DIY perspective is building a VTTC (vacuum tube Tesla coil) from scratch a few years ago. It was a great (and expensive) experience, and now I am ready for another challenge. I think I have been bitten by the fusor bug. I already have a few of the materials I need (a couple NSTs, HV diodes, variac) and my brother runs the welding shop at the local community college, so I have a semi-dependable supply of metal to build with. I am a sucker for anything high voltage, and this seems like the next project for me. I want to build a demo fusor to show to my science students (not actually fusing for safety sake), that I can use as a stepping stone to build an actual fusing fusor one day. It seems like this site is the best place to start!
Hello! I am happy to be here!
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Drew Scott
- Posts: 17
- Joined: Tue Dec 08, 2020 1:45 pm
- Real name: Drew Scott
Hello! I am happy to be here!
"The clearest way into the Universe is through a forest wilderness." - John Muir
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Dennis P Brown
- Posts: 3190
- Joined: Sun May 20, 2012 10:46 am
- Real name: Dennis Brown
Re: Hello! I am happy to be here!
Welcome; also, I see you have read all the rules and are starting off on a good foot.
A NST is good for a demo fusor and as for diodes, well, read a good bit on those not just here (see many FAQ's on this subject) but on the internet to learn about high voltage (HV) diodes; these semiconductor components have issues related to current, time response as well as frequncy reponse - all determined by what you need for a given supply. These topics along with your vacuum question are just the begining to the fun of learning about constructing fusors. With the fairly reasonably priced chinese precip supplies, a fusor is a lot cheaper now. Of course, one pays extra in learning the required special handling so as not to kill said supply but again, that is covered in the FAQ's.
A NST is good for a demo fusor and as for diodes, well, read a good bit on those not just here (see many FAQ's on this subject) but on the internet to learn about high voltage (HV) diodes; these semiconductor components have issues related to current, time response as well as frequncy reponse - all determined by what you need for a given supply. These topics along with your vacuum question are just the begining to the fun of learning about constructing fusors. With the fairly reasonably priced chinese precip supplies, a fusor is a lot cheaper now. Of course, one pays extra in learning the required special handling so as not to kill said supply but again, that is covered in the FAQ's.
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Drew Scott
- Posts: 17
- Joined: Tue Dec 08, 2020 1:45 pm
- Real name: Drew Scott
Re: Hello! I am happy to be here!
I want to create a demo fusor to begin with for several reasons.
A) I have several of the parts already
B) I want to use it in the classroom and it would be safer
C) It will be good practice for the real thing
D) It will cost less
I forgot to mention, I have several HV diodes as well that were scrounged from old microwave ovens. I am currently using one as a half-wave rectifier to charge a large capacitor bank. Hopefully I have enough of them to use for the fusor supply, but I need to build the enclosure first. I have already made a bit of progress on that front since yesterday! See the attached image. I have ordered two (one to use, one for spare) 5" dia x 6" tall x 0.275" thick pyrex tubes to sandwich in between the 1" aluminum plates. I still need to figure out a HV pass through and build my grid electrode. I was originally planning on using copper wire & solder, but after reading the FAQs it is clear that that will not work as the temp will be too high and will melt it. My brother has a TIG welder and is pretty good with it, so I will probably make the pieces for the grid and get him to TIG it together for me. After that I just need to purchase a vacuum pump. I found some on eBay for around 150$ that say they get down to 25 microns of pressure at 9cfm, which sounds like it will do the trick. Still also need a pressure gauge.
Thanks!
A) I have several of the parts already
B) I want to use it in the classroom and it would be safer
C) It will be good practice for the real thing
D) It will cost less
I forgot to mention, I have several HV diodes as well that were scrounged from old microwave ovens. I am currently using one as a half-wave rectifier to charge a large capacitor bank. Hopefully I have enough of them to use for the fusor supply, but I need to build the enclosure first. I have already made a bit of progress on that front since yesterday! See the attached image. I have ordered two (one to use, one for spare) 5" dia x 6" tall x 0.275" thick pyrex tubes to sandwich in between the 1" aluminum plates. I still need to figure out a HV pass through and build my grid electrode. I was originally planning on using copper wire & solder, but after reading the FAQs it is clear that that will not work as the temp will be too high and will melt it. My brother has a TIG welder and is pretty good with it, so I will probably make the pieces for the grid and get him to TIG it together for me. After that I just need to purchase a vacuum pump. I found some on eBay for around 150$ that say they get down to 25 microns of pressure at 9cfm, which sounds like it will do the trick. Still also need a pressure gauge.
Thanks!
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"The clearest way into the Universe is through a forest wilderness." - John Muir
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Dennis P Brown
- Posts: 3190
- Joined: Sun May 20, 2012 10:46 am
- Real name: Dennis Brown
Re: Hello! I am happy to be here!
Good progress but as for the vacuum pump, an ok unit for a simple demo. When a pump is 'good for' 25 microns, that tends to mean it will maybe get below 50 microns. That is rather marginal performance for a two stage pump. Might not work for a real fusor.
Microwave diodes won't necessarily handle a NST (under no load) since some NST units reach above 8 kV. Most such diodes will likely fail. Proper HV diodes are cheap so maybe consider proper valued ones (15 to 30 kV; even high current ones are cheap in this voltage range.)
Even a demo fusor plasma can harm a glass cylinder leading to implosive failure (throwing high speed glass fragments.) So to be safe make sure it is enclosed in a wire screen cage.
In the future, start any new threads and/or updates either in the New User Chat area or for photo's, Image du Jour.
Microwave diodes won't necessarily handle a NST (under no load) since some NST units reach above 8 kV. Most such diodes will likely fail. Proper HV diodes are cheap so maybe consider proper valued ones (15 to 30 kV; even high current ones are cheap in this voltage range.)
Even a demo fusor plasma can harm a glass cylinder leading to implosive failure (throwing high speed glass fragments.) So to be safe make sure it is enclosed in a wire screen cage.
In the future, start any new threads and/or updates either in the New User Chat area or for photo's, Image du Jour.